Mulberry's catwalk show, which takes place today at Claridge's, will be bittersweet for Emma Hill. It's her final one. She'll take her bow at the end, as usual. After that, her tenure as creative director will be over.

She wasn't thinking about that, though, when I interviewed her on Friday. Surrounded by her team (around nine designers who work on the bags and the ready-to-wear lines), most of them on a sugar high from a mountain of doughnuts, she was a paradigm of organised focus.

"There's an army of models waiting outside for their casting, a list of last-minute pieces still being made or FedEx-ed as I speak," she reported cheerfully.

"When you style the show, which we did on Wednesday, you often realise that you need extra bits, so that's when you email more designs to your factory. Everyone works round the clock in the final days. We'll be finalising the hair and make up a bit later." Unsurprisingly, she hasn't slept a huge amount this week.

But that's normal. The top models have been in New York the past week for the shows there. Some of them flew into London only yesterday: last-minute fittings are par for the course. But that's the way she likes it. It was Hill who introduced catwalk shows after she launched a clothing line to Mulberry, which until then had confined itself to luggage and bags. Although it still accounts for a small percentage of the company's revenue, the ready-to-wear line has been a key driver in its marketing.

"Without a catwalk show it's very hard for an accessories brand to create the kind of buzz you need these days to get international recognition. You need the catwalk in order to tell a story, and, really, to do catwalk, you need clothes."

On the positive side, that means it has enormous potential for growth, but also a conundrum on its hands. How does it appeal to a global audience without losing the quirkiness that makes it the favourite luxury bag choice for the domestic market?

The answer, according to Bruno Guillon, the chief executive who joined Mulberry last year from Hermès, is to make it more luxurious and exclusive. Inevitably there has been much industry speculation surrounding Hill's decision to quit. However, she is not about to tell tales.

"I've been here almost six years - the longest I've been anywhere. In that time the company has changed hugely," says Hill, who was christened Emma because her mother "wanted a daughter who could kick ass, like Emma Peel from The Avengers".

Having joined Mulberry the week before Lehman Brothers collapsed, she needed all of Peel's gumption. "It wasn't great timing," she says with some understatement, "but I like a challenge."

She rose to it, too. While Mulberry's sales tumbled at the end of 2008, they soon began to climb again, only hitting a wall in the past year, although some of the downturn in profits can be attributed to internal structural changes and a new factory in Somerset.

For her part, Hill has churned out a series of "It" bags, including the Alexa, as well as constantly reinventing the Bayswater, designed by Nicholas Knightly, her predecessor at Mulberry, and surely one of the bestselling British bags of all time. In 2012 she was awarded a CBE - "one of my proudest moments".

An instinctive designer, she says her secret is "not to look at the figures too much. I've always believed that if you come up with great design it will sell. Sometimes recessions can play to a brand's strength, if what you're doing is perceived to be authentic. Lots of people wanted to buy into a British label. We were doing classics, but they were a bit different and there's always been that feeling in this country that even if you economise on your clothes, you should have good accessories. I think what Mulberry represented was affordable luxury."

Many believe that Hill's vision of affordable luxury clashed with Guillon's luxurious luxury. Yet having worked in the past at Burberry, Marc Jacobs, Calvin Klein, Chloé and also Gap, it's clear she can turn her hand to all levels of the market.

She can't say where she'll be in a year's time. "But I'm not dropping off the face of the earth," she promises. She will, however, be heading for the pub straight after the show and then to a spa in Somerset, where coincidentally, Mulberry is opening a factory called The Willows; the company has decided that as a British brand, its goal is to increase its production of bags in the UK to 50 per cent of its total. Surely that's a change for the better?

While it has undoubtedly been a tough year for the company, with a dip in sales, Hill's resignation might, in the long term, turn out to be a positive for all concerned. Hill, who doesn't rule out a return to New York, where she lived for 13 years before coming home to London to join Mulberry, can surely have her pick of jobs now. Meanwhile, if Mulberry is to continue to expand, it needs to be bigger than a single creative director, however talented.

The billion-euro question is, can it become the global brand Guillon wants it to be? "The market is even tougher than it was five years ago," says Hill, "because there's far more competition. But Mulberry has got something really special. So, yes, it can - and I'll enjoy watching it grow".